Low temperature and broadband dielectric properties of V2O5 doped Mg2TiO4 ceramics

Abstract

The liquid phase effect of V(2)O(5) on the densification, microstructure and microwave dielectric properties of Mg(2)TiO(4) (MTO) ceramics has been investigated. The addition of V(2)O(5) significantly lowered the sintering temperature compared to pure MTO ceramics with improved microstructure, relative density and microwave dielectric properties. The increase in relative density and average grain size via growth of large grains and dissolution of small grains is explained by Ostwald ripening phenomena. Further, the microwave dielectric properties of the pure and MTO with V(2)O(5) samples were measured at cryogenic temperatures. It was observed that the loss tangent (tan ) and Q × f o of pure MTO increased with temperature, whereas the loss tangent and Q × f o of the samples with V(2)O(5) decreased with a rise in temperature. However, the MTO ceramics added with 0.5 and 1.0 wt% of V(2)O(5) manifested slightly higher loss tangents as compared to the pure MTO ceramics. The mechanism of the microwave loss is in agreement with the theory of intrinsic dielectric loss derived from the two phonon difference process. Further, the distinctive loss peak at 40 K is attributed to the orientation polarization having dispersion at the microwave frequency. The addition of V(2)O(5) did not cause any changes on the temperature stability of the MTO ceramics, whereas the temperature coefficient of the permittivity increases with an increase in temperature. The broadband dielectric measurement reveals that the V(2)O(5) doping increases the dielectric constant and enhances the stability over a wide frequency range, and shows a peak around 1.8 GHz. The tan of pure MTO still shows the peak whereas the samples doped with V(2)O(5) suppresses this peak significantly.